Carbon dioxide digital subtraction angiography: the practical approach

CO(2) has developed into a viable alternative to iodinated contrast for digital vascular imaging. Because CO(2) is a gas, it has a unique set of properties that affords certain advantages over iodinated contrast in a variety of settings. However, if CO(2) is used inappropriately, these same properties are associated with a unique set of rare but potentially harmful events. Therefore, it is essential that these unique characteristics be understood in order to employ a few simple precautionary measures. Fortunately, there is a delivery system currently available that is readily assembled and easy to use that ensures the appropriate administration of CO(2). This system, combined with experience, can reduce the greater labor intensity sometimes associated with CO(2) digital subtraction angiography. When it is used appropriately, CO(2) digital subtraction angiography alone or in combination with iodinated contrast offers diagnostic and interventional rewards that are not available with traditional intravascular contrast examinations.

Standardized measurement of the future liver remnant prior to extended liver resection: methodology and clinical associations

BACKGROUND

There is no agreement regarding the preoperative measurement of liver volumes and the minimal safe size of the liver remnant after extended hepatectomy.

METHODS

In 20 patients with hepatobiliary malignancy and no underlying chronic liver disease, volumetric measurements of the liver remnant (segments 2 and 3 +/- 1) were obtained before extended right lobectomy (right trisegmentectomy). The ratios of future liver remnant to total liver volume were calculated by using a formula based on body surface area. In 12 patients, response to preoperative right trisectoral portal vein embolization was evaluated. In 15 patients who underwent the planned resection, preoperative volumes were correlated with biochemical and clinical outcome parameters.

RESULTS

The future liver remnants increased after portal vein embolization (26% versus 36%, P < .01). Smaller size liver remnants were associated with an increase in postoperative liver function tests (P < .05) and longer lengths of hospital stay (P < .02). Preliminary data indicates an increase in major complications for liver volumes < or = 25% (P = .02).

CONCLUSIONS

A simple method of measurement provides an assessment of the liver remnant before resection. It is useful in evaluating response to portal vein embolization and in predicating the outcome before extended liver resections.

Internal jugular and upper extremity central venous access in interventional radiology: is a postprocedure chest radiograph necessary?

OBJECTIVE

The necessity of obtaining a postprocedure chest radiograph after central venous access using the upper extremity or internal jugular veins and interventional radiologic techniques was evaluated.

SUBJECTS AND METHODS

A prospective study of 937 consecutive central venous access procedures in interventional radiology using the internal jugular veins or upper extremities was performed from June 1995 through September 1997. Established interventional radiologic techniques were used to place various ports (n = 34) and tunneled (n = 670) and nontunneled (n = 233) catheters. All catheters were positioned using fluoroscopy and readjusted if necessary before termination of the procedure. Afterward, a chest radiograph was obtained with the patient upright to evaluate catheter position and possible procedural complications. Procedural complications and manipulations or interventions that resulted from the radiographic findings were noted. In addition, nursing time for acquisition of the chest radiograph was recorded.

RESULTS

We found seven procedural complications (four air emboli, two pneumothoraces, one innominate vein laceration) significant enough to alter the patient's treatment. These complications were apparent during the examination. Postprocedure chest radiography failed to reveal any unknown complications and revealed only one catheter sufficiently malpositioned to require manipulation. The amount of nursing time to acquire postprocedure chest radiographs ranged from 8 to 40 min (mean, 23 min) per patient.

CONCLUSION

When imaging guidance and interventional radiologic techniques are used for upper extremity and internal jugular central venous access, performing postprocedure chest radiography yields little benefit.

CO2 digital subtraction angiography for renal artery angioplasty in high-risk patients

OBJECTIVE

The efficacy of CO2 digital subtraction angiography for performing renal artery angioplasty in high-risk patients was evaluated.

SUBJECTS AND METHODS

From January 1997 to July 1998, 21 high-risk patients underwent 29 renal artery angioplasties using carbon dioxide as the principal contrast agent. Six patients had a known allergy to iodinated contrast material and 15 had elevated levels of creatinine. Iodinated contrast material was used only if necessary. All periprocedural allergic reactions were recorded. Before and 24 hr after the procedure, serum creatinine levels were obtained. If the creatinine level had become significantly elevated (>0.5 mg/dl), the creatinine level was acquired a second time.

RESULTS

Twenty-one patients (13 men and eight women) underwent 29 angioplasties (two were bilateral and six were repeated). Four kidney transplantation patients had ostial stenosis and the remaining 17 patients had nonostial stenosis. For all patients except one angioplasty initially was a technical success, as defined by a residual stenosis of less than 30%. Supplemental iodinated contrast material was used in only six patients (average dose, 8.5 ml). A range of 80-200 ml of carbon dioxide per procedure was used (average dose, 114.6 ml). One renal artery dissection occurred, which was unrelated to the carbon dioxide. There were no allergic reactions. The level of serum creatinine remained the same after 11 procedures, decreased after 12 procedures, and increased minimally after four procedures (<0.5 mg/dl).

CONCLUSION

On the basis of our preliminary findings in a small group of patients, using carbon dioxide as an intravascular contrast agent to perform renal artery angioplasty in patients who have an allergy to iodinated contrast material or who suffer from renal insufficiency is safe and efficacious.

Comparison of hepatic damage from direct injections of iodinated contrast agents and carbon dioxide

PURPOSE

This study guides the choice of contrast agent for localization of portal veins during transjugular intrahepatic portosystemic shunt (TIPS) placement or use in percutaneous transhepatic cholangiography (PTC) by providing gross anatomic and histologic comparison of effects from parenchymal injections of iodinated contrast agents and carbon dioxide.

MATERIALS AND METHODS

Eighteen New Zealand White rabbits received direct injections of 2-5 mL of either the nonionic contrast agent iohexol 300 mgI or the ionic contrast agent diatrizoate meglumine 60% into one lobe of the liver and the same volume of CO2 into the other lobe. The rabbits were killed at 2-7 days for gross and histologic evaluation of the livers.

RESULTS

At the time of injection, the diatrizoate and iohexol sites showed persistent dark discoloration, whereas CO2 sites showed minimal visible changes. On gross examination at death, all diatrizoate sites showed severe scarring and also commonly showed areas of necrosis. CO2 and iohexol sites showed only minimal discoloration and needle-puncture scars (P < .0001). The histologic grade for diatrizoate sites was significantly more severe than paired CO2 sites (P < .016). Iohexol sites showed mild histologic changes similar to paired CO2 sites (P = .375).

CONCLUSION

Iohexol and CO2 produce less severe hepatic damage and are preferred to meglumine diatrizoate for hepatic injection.

Carbon dioxide digital subtraction angiography for renal artery stent placement

PURPOSE

To determine the efficacy of renal artery stent placement with use of carbon dioxide as the primary contrast agent.

MATERIALS AND METHODS

Seventeen hypertensive patients with renal ostial stenosis were evaluated and underwent stent placement with use of CO2 digital subtraction angiography (DSA). Besides hypertension, 11 patients had decreased renal function, three had iodinated contrast material allergy, one patient had both, and two had neither. Supplemental iodinated contrast material (25 mL or less) was used in five patients. Preprocedure and postprocedure serum creatinine levels were obtained to evaluate the effect of CO2 on renal function. Arteriography was used to evaluate stent positioning.

RESULTS

Twenty-three Palmaz stents were placed in 17 patients. Six placements were bilateral, with a total of nine right and 14 left. No additional stents were required to correct malposition. One patient had a mildly significant, yet transient, rise in the postprocedure creatinine level. This patient received 10 mL of iodinated contrast material in addition to CO2. There were no allergic reactions.

CONCLUSION

The utilization of CO2 DSA facilitates the accurate placement of renal artery stents by eliminating the concern for contrast material-associated nephropathy and allergy. These attributes, coupled with the benefit of low viscosity, permit unrestricted imaging, guidance, and precise positioning not afforded by iodinated contrast material.

Interventional radiology placement of twin Tesio catheters for dialysis access: review of 75 patients

PURPOSE

To evaluate the safety and efficacy of modern interventional radiology techniques and imaging guidance for placement of jugular vein twin Tesio hemodialysis catheters.

MATERIALS AND METHODS

Eighty-two sets (75 patients) of twin Tesio catheters were percutaneously placed in the right (n = 70) and left (n = 12) internal jugular veins with use of ultrasound (US) and fluoroscopic guidance. Immediate procedural and late complications were recorded. The efficacy of the Tesio system was also evaluated.

RESULTS

With US and fluoroscopic guidance, the technical success for access and catheter placement was 100%. Measured dialysis blood flow rate of greater than 375 mL/min was obtained in 95% of the patients and recirculation averaged 4.6% +/- 5%. An inadvertent common carotid artery puncture occurred in one (0.6%) patient and prolonged exit site bleeding occurred in another five patients (3%). Each of these was successfully controlled with compression. More chronically, catheter thrombosis and exit site infection occurred each at the rate of 0.16 episodes per 100 catheter days. All thrombosis and exit site infections responded to local thrombolysis and antibiotic therapy, respectively. Bacteremia occurred in 20 patients and required catheter removal in five patients. There was no clinical evidence of upper extremity or superior central vein thrombosis.

CONCLUSION

Placement of internal jugular, twin Tesio catheters with use of imaging and interventional techniques provides a safe and efficacious means of either short or long-term hemodialysis.

Sonographic guidance when using the right internal jugular vein for central vein access

OBJECTIVE

The intent of this study was to substantiate the advantages of the use of sonographic guidance for central venous access via the right internal jugular vein.

SUBJECTS AND METHODS

Eighty sequential patients requiring central vein access were examined with a hand-held sonography transducer to determine the size, patency, and location of the right internal jugular vein before puncture. Access to the right internal jugular vein was subsequently performed, under sterile conditions, using sonographic guidance. Periprocedural complications were prospectively recorded. Subsequently, we compared our findings with published reports of complications when visible and palpable anatomic landmarks were used for guidance during cannulation of the internal jugular vein.

RESULTS

Among these 80 patients, the anatomy of the right internal jugular vein was typical in only 57 (71%). In another 13 patients (16%), sonography showed a medial position of the right internal jugular vein, anterior to the common carotid artery. In three other patients (4%), the right internal jugular vein was positioned laterally by more than 1 cm. In the remaining seven patients (9%), the vein was thrombosed. Its diameter, measured without use of the Valsalva maneuver, also varied, measuring 0.5-2.0 cm. Cannulation was achieved in all 73 patients with a patent right internal jugular vein. One puncture was required in 68 patients (93%); two punctures in three other patients (4%); and three punctures in the remaining two patients (3%). In no case was the common carotid artery inadvertently punctured. Only one periprocedural complication occurred, and it was unrelated to the use of sonographic guidance.

CONCLUSION

Sonographic guidance for central vein access via the right internal jugular vein is safer and more efficient than the traditional landmark approach.

Angiography with carbon dioxide (CO2)

CO2 possesses many advantages over conventional iodinated contrast agents used for arteriography. It is nonallergic and lacks renal toxicity. Its unique properties permit use of smaller catheters in diagnostic and therapeutic angiographic procedures, allow optimal vascular imaging of various neoplasm, assist in detection of occult gastrointestinal bleeding, and facilitate TIPS procedures. With digital subtraction techniques and stacking programs, CO2 arteriography is as accurate as iodinated contrast studies in most patients and thus is the preferred arterial imaging technique in patients with contrast allergy and renal insufficiency. CO2 is also extremely inexpensive compared with available contrast agents. Understanding of the effects of buoyancy and compressibility is necessary for safe, controlled delivery of CO2 during arteriography, but only rare complications have occurred in our large experience with CO2 angiography. Thus, use of CO2 as an arterial contrast agent significantly expands the safety and utility of arterial imaging in patients with peripheral vascular disease.

Carbon dioxide (CO2) digital subtraction angiography: 26-year experience at the University of Florida

Although the vascular system is presently being imaged by multiple high technology modalities, contrast angiography continues to be the gold standard; however, severe complications rarely occur. During the last 25 years (in over 1400 patients), CO2 has proven to be extremely safe (no allergy or renal failure). However, it is imperative to understand CO2's physical properties and potential dangers. Recently, CO2 is being routinely utilized not only because of safety, but for detection of minute amounts of bleeding, better collateral filling, and for most interventional procedures since unlimited volumes of CO2 can be injected between the catheter and guidewire. Presently, safe, reliable and "user-friendly" delivery systems are now commercially available. CO2 DSA images are now nearly comparable to iodinated contrast, and improvement in DSA images are evolving, including "stacking" software.

Examination of renal donors as outpatients using intraarterial digital subtraction angiography and a pigtail catheter

OBJECTIVE

We performed this study to assess the safety and efficacy of outpatient angiographic renal donor examination using a 3-French pigtail catheter, intraarterial digital subtraction angiography, and a progressively shortened examination time after the procedure.

CONCLUSION

For 45 consecutive procedures performed, no complications were reported, and no diagnostic discrepancies were found in patients who proceeded to surgery. Using this method we were also able to eliminate the excretory urogram as well as reduce the total amount of contrast per procedure.

Long-term performance and complications of the Tesio twin catheter system for hemodialysis access

The Tesio twin catheter system (Medcomp, Harleysville, PA) was developed to overcome the problems with the existing central venous catheters in providing high-efficiency dialysis, such as inadequate blood flows, high recirculation rates, and need for surgical insertion. The relatively large internal lumens and multiple side holes in a spiral pattern allow for high blood flow rates and lower tendency to thrombosis. In this series, 82 catheter pairs were placed in 75 patients and monitored for a period encompassing 231 patient-months. We achieved mean nominal blood pump flow rates of 400 +/- 6 mL/min and an average recirculation of 4.6% +/- 0.5%. In 20 sets of catheters, a nominal blood flow rate of 388 +/- 6 mL/min was measured ultrasonically at 352 +/- 8 mL/min, representing an error of 36 +/- 5 mL/min. Thrombosis of the catheter occurred at a rate of one episode per 21 patient-months, and on all occasions responded to local instillation of urokinase. Despite having two exit sites, the infection rates were comparable to other catheters: exit site infections occurred at a rate of one per 21 patient-months and bacteremic episodes occurred at one per 11.5 patient-months, necessitating catheter removal once per 46 patient-months. Based on these data, we believe that the Tesio twin catheter system is an excellent long- and short-term vascular access for providing high-efficiency dialysis.

Button self-retaining drainage catheter

To help improve patient acceptance of long-term internal/external catheter access to the biliary tract in those with benign biliary obstruction, a simple design allows the catheter end to remain flush with the skin. It consists of a clothes button affixed to the drainage catheter with a wood screw after the catheter has been cut off at the skin exit. This button/screw device has been used successfully in 22 patients over the last 10 years; catheter exchanges were easily accomplished.

Effects of carbon dioxide arterial infusion on hepatic biochemistry and histology in a rabbit model

RATIONALE AND OBJECTIVES

The objective of this study was to determine the effect of carbon dioxide (CO2) infusion on hepatic biochemistry and histology in a rabbit model.

METHODS

The study population consisted of 24 anesthetized rabbits that received hepatic infusion of either CO2 or saline (control) at doses of 10 mL/kg, comparable with those doses used in human clinical trials. Blood for clinical chemistry analysis was collected at baseline, 1 hour, 24 hours, and 168 hours (7 days) postprocedure. The rabbits were killed at 7 days postprocedure and the liver examined histologically for hepatic damage.

RESULTS

There were no significant differences between the CO2 and the control groups in dorsal, ventral, and dorsal/ventral scores. Increases in alanine, an important indicator of hepatocellular membrane injury, in the CO2 group were significantly greater at 1 hour and 24 hours posttreatment (P = 0.037 and 0.013). However, the mean levels at 168 hours (7 days) were not significantly different (P = 0.22). The increases at 1 and 24 hours were small, transient, and considered clinically insignificant.

CONCLUSION

No long-term hepatic effects in these animals were suggested by biochemical and histological examinations.

Carbon dioxide digital subtraction angiography: expanding applications and technical evolution

Although several noninvasive techniques now exist for vascular imaging, including MR imaging, three-dimensional CT, and color-flow and duplex sonography, the gold standard to which these techniques are compared remains catheter angiography. Cut-film and digital subtraction angiography (DSA) using iodinated contrast material are the standard methods by which vascular imaging is performed. However, despite the development of low-osmolar contrast agents, premedication regimens, and careful patient selection, adverse reactions to contrast material, including idiosyncratic reactions and contrast-induced nephropathy, continue to occur in a small number of patients [1-3]. Carbon dioxide (CO2) was developed as an alternative to iodinated contrast material to avoid these problems [4]. Once the behavior of intravascular gas, the methods of safe delivery, and the principles of successful imaging are understood, the use of CO2 as an intravascular contrast agent during DSA allows accurate imaging with little risk. Recent advances in delivery systems, postprocessing capabilities, and its extension to new vascular interventional procedures have greatly expanded the usefulness of CO2 angiography in both diagnostic and interventional vascular radiology.

Current status of carbon dioxide angiography

The current status of carbon dioxide as an angiographic contrast agent is reviewed in this article. The physical characteristics of intravascular carbon dioxide, pertinent physiology, and principles of imaging are discussed. In addition, the advantages and limitations of carbon dioxide are compared with those of iodinated contrast. Examples of diagnostic and therapeutic procedures in both the arterial and venous systems show the utility of carbon dioxide angiography.

CO2 digital angiography: a safer contrast agent for renal vascular imaging?

Although the new nonionic contrast agents are safer than ionic agents, renal insufficiency and even death still occur occasionally. Therefore, we have explored the use of carbon dioxide (CO2) as an alternative angiographic contrast agent used in combination with digital subtraction angiography. Clinical observations have been made in over 800 patients. The images obtained are of equivalent diagnostic quality compared with those using conventional iodinated contrast agents. Recent advances in imaging, including "stacking," provide images comparable with iodinated contrast. Very small vessels, equivalent to third-order branches of the renal artery, can be imaged satisfactorily with CO2. Occasional studies with CO2 yield information not apparent with iodinated contrast agents, including excellent visualization of arteriovenous shunts, collateral circulations, malignant tumors, and minute amounts of arterial bleeding. Many of the advantages and disadvantages of CO2 derive from its special physical and chemical properties. The advantages include no allergic potentiation and no renal metabolism of CO2, because CO2 is cleared by the lungs and does not recirculate. Other advantages include delivery by very small catheters because of the low viscosity of CO2, minimal discomfort on injection, and very low cost. However, the low-density and compressibility of CO2 poses some special problems. Imaging requires digital subtraction angiography with electronic enhancement and injections require an experienced investigator and, ideally, a dedicated CO2 injector. The dedicated CO2 injector provides calculated, controlled dosing and rates for injection, while excluding the possibility of air contamination. The buoyancy of CO2 inhibits good filling of dependent vessels. Accordingly, CO2 does not normally produce good nephrographic images, although proximal renal arteries are normally shown clearly. Experimental studies in dogs, whose renal arteries have been injected repeatedly with very large doses of CO2, demonstrate only transient changes in renal blood flow and no endothelial cell damage. However, these studies also showed clearly that renal ischemia can occur due to a "vapor lock" phenomenon if the kidney is positioned vertically above the injection site, and recurrent injections are given without time for absorption of the arterially delivered CO2 boluses. Uncontrolled studies in over 800 patients have confirmed that CO2 likely has a very low renal toxicity. At the University of Florida, CO2 is the radiologic contrast agent of choice in patients with renal insufficiency, especially those with diabetes mellitus, and in those with pre-existing allergy to iodinated contrast agents. Further controlled clinical studies are required to define the true clinical utility and safety of CO2 compared with conventional radiologic contrast agents.

Permanent indwelling peritoneal access device for the management of malignant ascites

The case presented demonstrates an alternative management approach for malignant ascites. A permanent indwelling peritoneal port for at-home, small-volume paracentesis, provided palliative therapy for a patient who had malignant ascites secondary to breast cancer. The device allowed paracentesis without the risk of repetitive peritoneal puncture or diuretic therapy.

Mediastinal mass and tracheal compression due to an aneurysm of a systemic-to-pulmonary collateral artery in a patient with pseudotruncus arteriosus

A patient with pseudotruncus arteriosus who presented with a large mediastinal mass due to a systemic-to-pulmonary collateral artery aneurysm is reported. This aneurysm caused tracheal compression with resulting dyspnea and postobstructive pneumonitis, which are unusual presenting features in these patients. The differential diagnosis for a mediastinal mass arising in a patient with pseudotruncus arteriosus, or any other patient with possible systemic-to-pulmonary collateral arteries, should include aneurysm.

Short-term effects of selective renal arterial carbon dioxide administration on the dog kidney

PURPOSE

The authors examined the nephrotoxicity of carbon dioxide injected directly into the renal arteries as an arterial contrast agent.

MATERIALS AND METHODS

Fourteen anesthetized dogs received selective renal infusions of CO2 ranging from a normal dose of 7 cm3/kg to high doses of 11-54 cm3/kg. Two dogs received conventional iodinated contrast media. The effects on renal function and histologic appearance were evaluated by means of radionuclide studies (iodine-131 iodohippurate sodium and technetium-99m dimercaptosuccinate) and histopathologic examination (light, transmission, and scanning electron microscopy).

RESULTS

Although there was a mean decrease in renal blood flow of 11.86% (standard error [SE], 7.1) immediately after the injection of CO2, flow had returned to baseline (0.17%; SE, 5.27) after 24 hours. Although the sample size was small, there was no dose-dependent effect of CO2 on renal function and histologic appearance. Mild histologic changes and one case of moderate acute tubular necrosis were seen only in cases in which the kidney was positioned vertically rather than laterally.

CONCLUSION

Although formal studies in patients are required, the results of this investigation suggest that CO2 may be a safe contrast agent and less nephrotoxic than existing contrast agents, providing care is taken to ensure that CO2 is not trapped in a vertically positioned kidney, as might occur in renal transplant recipients.

Captopril renography and the hypertensive renal transplantation patient: a predictive test of therapeutic outcome

PURPOSE

To detect predictive accuracy of captopril renography in transplant recipients with hypertension.

MATERIALS AND METHODS

This prospective study was performed to evaluate findings on 18 renal scans acquired after administration of captopril (captopril renograms) in 14 transplantation patients with new-onset or poorly controlled hypertension. Captopril renography was not used to affect case management but to predict response to angioplasty.

RESULTS

Arteriograms were abnormal in 12 of 18 studies. In the six cases in which angiograms were normal, captopril renograms also were normal. In the 12 cases in which angiograms were abnormal, captopril renograms were normal in five and abnormal in seven. In the five cases in which renograms were normal, hypertension did not improve, although angioplasty was technically successful. In the seven with abnormal renograms, four patients underwent angioplasty with excellent results. These patients had a significant (P < .05) decrease in diastolic blood pressure (-15 mm Hg) and in creatinine concentration (-0.4 mg/dL) compared with patients with normal renograms and abnormal angiograms.

CONCLUSION

In this small population, captopril renography appeared to be predictive of physiologically meaningful renal artery stenosis.

Follow-up evaluation after renal artery bypass surgery with use of carbon dioxide arteriography and color-flow duplex scanning

PURPOSE

Postoperative evaluation of renal artery bypass grafts historically has been obtained by contrast renal arteriography before discharge from the hospital. Recent reports have advocated replacing arteriography with abdominal duplex scanning for evaluating and monitoring the integrity of renal artery bypasses. We propose a combination of these two techniques, which provides minimal risk to the patient and renal parenchymal function.

PURPOSE

Between July 1, 1990, and Dec. 31, 1991, 17 patients (8 men, 9 women) underwent 24 renal artery bypasses for poorly controlled hypertension or deteriorating renal function. In the immediate postoperative period each patient underwent carbon dioxide (CO2) renal arteriography to detect any technical defects and to define bypass graft anatomy. Subsequently, color-flow duplex scanning of the renal artery bypass grafts were done at 3-month intervals with the postoperative CO2 arteriogram for baseline comparison. CO2 arteriography clearly defined proximal/distal anastomotic anatomy, bypass conduit integrity, and bypass conduit runoff.

RESULTS

Procedural morbidity was zero because no hematomas developed and serum creatinine remained stable. Duplex scanning for a mean follow-up of 8.3 months revealed antegrade flow in 23 bypasses with peak systolic velocity of 60 to 100 cm/sec. One bypass graft had a peak systolic velocity greater than 150 cm/sec suggestive of a proximal anastomotic stenosis; however, the patient died before a repeat, verifying CO2 arteriogram could be obtained. Recurrent hypertension developed in one patient with velocities less than 100/cm/sec, and repeat CO2 arteriography revealed no evidence of graft or anastomotic stenosis.

CONCLUSION

CO2 arteriography and duplex scanning provide an accurate means of initially evaluating and subsequently monitoring renal artery bypass grafts, with minimal risk of renal or patient morbidity.

Carbon dioxide gas as an arterial contrast agent

OBJECTIVE

To investigate the clinical utility of CO2 gas as an arterial contrast agent, the experience with CO2 arteriography at the University of Florida was reviewed.

SUMMARY BACKGROUND DATA

Preliminary studies have demonstrated the feasibility of CO2 arteriography and shown that arterial injection of CO2 gas appears non-toxic (which could limit the risks of contrast induced renal injury and allergic reaction). However, numerous technical problems make CO2 arteriography a demanding technique and recent studies have suggested that distal lower extremity vessels are difficult to image using CO2 arteriography, especially when significant arterial occlusive disease is present.

METHODS

One hundred twenty-eight CO2 arteriograms done in 115 patients were reviewed. CO2 arteriograms were graded as excellent, good, poor, or inadequate by two blinded observers and results of CO2 studies compared to results of standard contrast studies (done in 98 patients for image comparison). In addition, a therapeutic plan based on the CO2 arteriograms was compared with the therapy each patient received.

RESULTS

One hundred-seventeen (91%) of the CO2 arteriograms were of good or excellent quality and agreement between CO2 studies and standard contrast studies was seen in 93 of 98 cases (95%). Accurate therapeutic plans based on CO2 studies were possible in 92% of cases with inadequate visualization of infrapopliteal arteries being the major limitation (7 cases). No allergic reactions occurred and only one patient potentially had contrast-induced nephrotoxicity.

CONCLUSIONS

CO2 arteriography provides accurate, clinically useful arterial imaging with minimal risk. Thus, this new technology significantly increases the utility of arteriography in patients with peripheral vascular disease.

Angiography of the lower extremity in atherosclerotic vascular disease. Current techniques

With the vast array of technology available, detailed diagnostic information is now routinely obtained in patients with peripheral vascular disorders. In addition, percutaneous intervention and advanced surgical techniques now safely permit the patient to return to an active life, and in advanced vascular disease, the extremity can be salvaged when previously the only option was amputation. We feel strongly that the maximum amount of information about the arterial system should be obtained throughout the patient's management. In addition, these complex procedures require considerable experience and judgment, and our practice of ongoing communication with the vascular surgery staff during both the diagnostic and the therapeutic phases of the patient's treatment has been extremely beneficial.

Carbon dioxide as an angioscopic medium. Comparison to various methods of saline delivery

The limitations of angiography, when it is used as the sole method of vascular assessment, are increasingly apparent as vascular intervention becomes more sophisticated. Angioscopy could be an adjunctive diagnostic modality by differentiating among thrombus, dissection, and atheroma, and by monitoring the response to therapy. However, angioscopy requires a blood-free field for adequate visibility, and this may be difficult to obtain. The feasibility of carbon dioxide (CO2) and various saline delivery methods for clarifying the viewing field for percutaneous angioscopy was investigated. Angioscopy of femoral and iliac arteries on nine dogs was performed. Saline was infused by hand injection, pressure bag infusion, or mechanical power injection, and CO2 gas was injected using a special gas injector. The clarity of the viewing field was graded for each medium and method. Excellent quality antegrade femoral angioscopy was obtained with CO2. The superiority of CO2 injection in comparison with power-injected saline approached statistical significance (P = .06). Power-injected CO2 and power saline were superior to hand-injected or pressure bag-injected saline for maintaining sufficient visibility. Retrograde iliac angioscopy was possible without inflow occlusion, but required high flow rates (only possible with power-injected saline or CO2). CO2 injected under controlled circumstances holds promise as a medium to improve angioscopic visibility.

Dynamic CT of hepatic masses using intraarterial enhancement: advantages and pitfalls

Forty-two patients were evaluated by dynamic incremental computed tomography (CT) following transcatheter infusion of contrast material into the celiac and hepatic arteries. Most of these patients had liver metastases from colorectal carcinoma, but the series also included two cases of hepatic hemangiomas, one case of granulomas due to atypical mycobacterium, and two cases of retroperitoneal tumors involving the liver. Several distinct patterns of liver opacification were recognized, reflecting differential perfusion of hepatic lobes during selective intraarterial contrast enhancement. The spectrum of observed findings, as well as the advantage or limitations of this technique, are described.

A solution to the problem of high-flow jets from miniature angiographic catheters

In this study we evaluated methods for reducing high-flow jets from 5-French catheters that occur when injection pressures approach catheter tolerance (1000 psi [6.9 MPa]). This "jet effect" has been responsible for subintimal extravasation of contrast material in patients. We designed a physical model that accurately measures flow rates through the end hole and each side hole of 5-French high-flow catheters under simulated physiologic arterial pressure. When a standard catheter commonly used for injection of contrast material was studied, flow of contrast material was 34% through the end hole and 31% through the distal side-hole pair at high injection pressures (1000 psi). We examined the effect of altering the size and configuration of catheter side holes and end hole in an effort to create an improved flow profile, and thus a safer angiographic catheter. End-hole flow rate was reduced by 73% to 9% of total flow by tapering the 5-French catheter to 0.018 in. (0.046 cm) and by using smaller 0.015-in. (0.038-cm) side holes for even flow distribution. The high-flow jets present with standard high-flow 5-French catheters do not occur when flow-restrictive end holes and side holes are used. A uniform flow profile can be obtained without sacrificing delivery of contrast material through small catheters.

Guide-wire reinforcement and lengthening with coaxial locking guide wires: the crimping technique

The authors developed a technique to increase the size of a guide wire and permit single-step placement of catheters and large sheath systems over previously inserted small-caliber guide wires. The technique involves compression of metal cannula against a smaller in-dwelling wire or inner cannula. It has been used successfully during laser-assisted balloon angioplasty and percutaneous nephrolithotomy.

New high-flow "cloud" catheter for safer delivery of contrast material

The authors describe a new angiographic catheter, which delivers equal flow rates through the side holes and reduced flow through the end hole compared with conventional catheters. Computer analysis of catheter-flow models revealed that placement of larger side holes proximally and smaller side holes distally produces more uniform flow rates out of the holes. This decreases the risk of potentially hazardous delivery of high-pressure jets of contrast material from the end hole. The flow pattern is so uniform that it resembles a cloud of contrast material on injection. This catheter design is particularly applicable for 3-5-F catheters, which require high-pressure injections. Clinical testing in 50 cases revealed no extravasations or unintentional selective injections with use of this catheter.

Miniaturization of catheter systems for angiography

Miniature techniques offer many advantages for performance of routine angiography, as well as invasive vascular procedures. On the basis of the authors' experience with over 16,000 diagnostic and interventional procedures, this report describes the equipment and methods used for miniangiography. Development of sturdy, high-flow 3-5-F catheters and 0.014-0.018-inch guide wires, combined with the use of small needle puncture techniques, has improved the safety of angiography and intervention such that outpatient procedures are now routine. Miniature catheter systems are now preferable to larger catheter systems in most instances.

The use of carbon dioxide gas to displace flowing blood during angioscopy

Carbon dioxide (CO2) gas is a safe and effective arterial contrast agent that images arteries by displacing blood. The use of CO2 gas to displace blood during angioscopy may improve intraoperative angioscopy and allow percutaneous angioscopy. To study this, 46 angioscopic evaluations in the femoral arteries of four dogs were done without inflow occlusion. The ability of CO2 gas to clear the flowing blood was compared to a high-pressure infusion of saline solution. Carbon dioxide gas successfully displaced flowing blood in 20 of 25 evaluations (80%) as compared to three of 21 evaluations (14%) with infusion of saline solution (p less than 0.0001). After the CO2 gas infusion was stopped, the image remained clear for 9 +/- 1 seconds. When saline was used, the image was clear only as long as the infusion was continued. The quality of clear images for the two media were similar through the eyepiece of the angioscope, but images observed through the motion picture camera had better contrast and depth of field in CO2 gas. The use of a CO2 gas infusion can clear the field of flowing blood without the risk of volume overloading and potentially allow performance of a successful percutaneous angioscopy.

Absolute ethanol renal angioinfarction for control of hypertension

Six patients (11 renal units) underwent ethanol renal angioinfarction for medically uncontrollable hypertension. The mean preablation blood pressure was 175/112 mm Hg despite antihypertensive medications. Five of the patients demonstrated elevated renal vein renin levels prior to angioinfarction. Hypertension was improved in all 6 patients, during a mean follow-up period of fifty-one months. Systemic hypertension was completely eliminated in 4 patients. Two patients continue to require antihypertensive medication to control their hypertension. There were no major complications directly related to intra-arterial injection of ethanol. Transcatheter renal ablation employing intra-arterial injection of absolute ethanol for control of severe hypertension appears to be a safe and efficacious procedure. It should be considered an alternative to nephrectomy in selected high-risk patients.

A phase II study of the efficacy of diamminedichloroplatinum (cisplatin) for the control of locally recurrent and intransit malignant melanoma of the extremities using tourniquet outflow-occlusion techniques

A phase II trial was conducted with 15 patients (mean age of 65.7 years) with locally recurrent or intransit melanoma of the extremities. After total outflow occlusion with pneumatic tourniquet, the cell-cycle nonspecific anti-neoplastic agent cis-diamminedicholoroplatinum (CDDP) was infused intra-arterially in a mean dose of 26.7 mg/m2 per infusion (2.6 infusions per patient). The aim of this study was to determine the efficacy of CDDP infusion for control of intransit and recurrent melanoma of the extremities. Three to four weeks postinfusion, all visible residual disease was resected. Partial remissions were observed in ten patients (67%); five patients achieved stable disease status. No patient had complete regression of disease. At an average follow-up interval of 18.3 months (range 4-44 months), the mean local/regional disease-free survival was 14.8 months. Eighty per cent of patients (twelve of 15) had local/regional control of disease at an average follow-up of 14.8 months after CDDP infusion and surgical resection. Of five melanoma-related deaths, three patients had had no local/regional recurrence at the time of their demise. Three compartment syndromes resulted as a complication of the infusional therapy and occurred within 1-3 days of the treatment. In vitro growth of melanoma from lymph nodes draining the infused area was seen in all subjects studied. Outgrowth from tumor within the tourniquet infusion area was observed in two patients, both of whom experienced recurrences clinically at 24-months' postinfusion. Pharmacokinetic data of total CDDP concentrations from tissue and blood (n = 4) were available from pretreatment to 1 hour post-therapy. Biopsy data from patients pre- and post-treatment suggest substantial tumor uptake of CDDP as compared to local or distal normal skin, with minimal CDDP loss to the systemic circulation. Pharmacologic and clinical data of this phase II trial suggest that intraarterial infusion with tourniquet outflow-occlusion augments tumor tissue levels of CDDP within the infused extremity and enhances local control of high-risk and intransit disease.

Effect of CO2 and blood media on laser probe temperature

Blood may limit laser ablation of arterial plaque by decreasing thermal energy transfer from metal-capped probes to arterial occlusions. Since a gas is a good insulator of heat, CO2 may be a better medium for laser recanalization. To study this possibility, a metal-capped fiber was positioned in a segment of blood-filled polyethylene tubing and activated with an argon laser. Probe temperatures were measured in blood and as the blood was displaced by flowing CO2 gas. Probe temperatures were higher at all powers studied in CO2 gas than in blood. Maximum probe temperatures averaged 518 +/- 24 degrees C after CO2 infusion versus 320 +/- 7 degrees C in blood, (P less than 0.0001). Blood aggregate formation was noted on the probe surface in blood but not in CO2 medium. Thus CO2 gas may be a preferable medium for laser recanalization, since higher probe temperatures are achieved, and the probe surface remains free of insulating blood coagulate.

Retractable-barb needle for breast lesion localization: use in 60 cases

A needle system with a retractable barb was developed for localization of nonpalpable breast lesions. The system can be repositioned without major adjustments and strongly anchors to breast tissue, eliminating failure due to dislodgment or transection of the localizing wire. Its use may necessitate fewer confirmatory radiographs, resulting in decreased radiation exposure. In addition, the needle can be retracted during surgery, to ease extraction of the specimen.

Directional needle for antegrade guide wire placement with vertical arterial puncture

A directional needle with a closed pencil-point tip and a distal side hole was developed to permit antegrade guide wire placement by way of a 90 degrees puncture angle. It has been used in over 25 patients without technical difficulties or complications. It has been very effective for catheterization of the superficial femoral artery for angioplasty, diagnostic studies, and chemotherapy infusion, providing easy antegrade access in patients in whom the traditional antegrade approach may be difficult.